One exemplary information recording medium having a sector structure is a hard disc. Hard discs, which are increasing more and more in memory capacity and used for multimedia contents, are applied in wider fields including personal computers and various consumer apparatuses.
Hereinafter, simultaneous recording and reproduction in a conventional hard disc will be described with reference to the figures. In hard discs, the size of recording and reproduction areas is pre-fixed to be a unit larger than a sector, and access is performed in units of fixed-size block.
FIG. 2 shows a model for simultaneously recording and reproducing a plurality of pieces of real time data. This model includes a pickup 74 for recording real time data to and reproducing real time data from an information recording medium, an encoder 70 for encoding first real time data, a recording buffer 72 for temporarily storing the encoded first real time data before the first real time data is recorded by the pickup 74, a reproduction buffer 73 for temporarily storing second real time data which is reproduced by the pickup 74, and a decoder 71 for decoding the second real time data which is transferred from the reproduction buffer 73.
FIG. 30 shows an example in which two pieces of real time data are simultaneously recorded and reproduced while ensuring continuity using the recording buffer 72 and the reproduction buffer 73. In this example, while the first real time data is recorded in areas 81 and 84 of an information recording medium, the second real time data which is recorded in areas 83 and 85 of the information recording medium is reproduced.
In FIG. 30, A81, A82 and A83 refer to operations of the pickup 74 of moving between areas to be accessed (access operations). It is assumed here that the time required for each of the access operations A81, A82 and A83 is a time period required for the pickup 74 to move between an innermost area and an outermost area of the information recording medium (i.e., the maximum access time Ta). It is also assumed that the data transfer rate between the pickup 74 and the recording buffer 72 and the data transfer rate between the pickup 74 and the reproduction buffer 73 are a constant rate Vt. It is also assumed that the data transfer rate between the encoder 70 and the recording buffer 72 and the data transfer rate between the decoder 71 and the reproduction buffer 73 are a constant rate Vd. In the case where the data to be recorded and reproduced is compressed at a variable rate, Vd is the maximum value of the range in which the rate is variable.
In a recording operation W81, data accumulated in the recording buffer 72 is all recorded in the area 81. Then, data is accumulated in the recording buffer 72 during the access operation A81, a reproduction operation R81 and the access operation A82. In a recording operation W82, data accumulated in the recording buffer 72 is all recorded in the area 84. Then, data is accumulated in the recording buffer 72 during the access operation A83, a reproduction operation R82 and the next access operation (not shown).
During the recording operation W81 and the access operation A81, data accumulated in the reproduction buffer 73 is consumed, and data is accumulated in the reproduction buffer 73 during the reproduction operation R81. Then, during the access operation A82, the recording operation W82 and the access operation A83, data accumulated in the reproduction buffer 73 is consumed, and data is accumulated in the reproduction buffer 73 during the reproduction operation R82.
In the case where the transfer rate of the data to be recorded and the transfer rate of the data to be reproduced are each constant, the data amount in the recording buffer 72 is balanced between a recording state and a non-recording state. The data amount in the reproduction buffer 73 is also balanced between a reproduction state and a non-reproduction state. Since the recording of the first real time data and the reproduction of the second real time data are performed alternately, the two pieces of real time data can be recorded and reproduced continuously.
The example shown in FIG. 30 shows a condition for the minimum size of the areas in which data can be recorded and reproduced. Namely, since it cannot be defined where in the information recording medium (disc) the areas for recording and reproduction exist, the access between the recording area and the reproduction area is considered based on the maximum access time including the time period until the rotation rate of the disc becomes a desired value.
FIG. 31 shows a transition in the data amount in the recording buffer 72 and the reproduction buffer 73 while the data is recorded and reproduced at a variable rate. In the case where data of more than or equal to the size of the recording area is not accumulated in the recording buffer 72 at the time of termination of a series of operations of: a recording operation W91, an access operation A91, a reproduction operation R91 and an access operation A92; a low recording rate results in the state where there is no sufficient data to be recorded. Thus, the recording operation is temporarily interrupted, which extends the time required for recording. In this case, an access operation A93 is performed for accessing an area next to the area in which real time data has been recorded, and thus a reproduction operation R92 is performed. In the case as described above where the data is recorded and access is performed, both in units of fixed-size block, the memory size required for the recording buffer 72 is a sum of the amount of data accumulated during the two access operations and one reproduction operation and the size of the fixed block. The reproduction buffer 73 needs to have the same memory size as that of the recording buffer 72.
In the case of a hard disc, data transfer capability is high. Therefore, the size of the fixed block can be reduced and the size of the buffer memory can also be reduced.
However, when the above-described system of simultaneous recording and reproduction is applied to an optical disc, there is a problem in that a large buffer memory is necessary. The reasons are that the data transfer rate of the optical disc is low and the access time is long. In order to perform simultaneous recording and reproduction for a disc having data recorded thereon by a different apparatus, there is another problem that compatibility needs to be ensured for stable simultaneous recording and reproduction.